Development of conduction-cooled superconducting coils having good processing and high thermal conduction plastic bobbins

超导线圈的电阻在极低的温度下变为零，因此，超导线圈的冷却方法是浸泡在液氦等低温液体中。另一种冷却方法是电冰箱的传导冷却。由于超导线圈仅通过制冷机冷头的传导来冷却，因此从线圈稳定性的角度来看，结构材料的导热性非常重要。我们提出了一种高导热塑料作为结构材料，其名称为Dyneema纤维增强塑料（DFRP）。DFRP具有随温度降低而热膨胀的特性。制作了以DFRP为芯轴的小型超导线圈，用制冷机冷却，并测量了线圈的稳定性。并制作了与氮化铝和玻璃纤维增强塑料（GFRP）相同规格的线圈，并对其稳定性进行了比较。实验数据表明，在线圈缠绕张力较大的情况下，线圈对结构材料的传热变好，DFRP线圈的稳定性与AlN线圈的稳定性相似或更好。

Electric resistance of superconducting coils becomes zero at extremely low temperature, and hence cooling method of the coils is immersing in low-temperature liquids such as liquid helium. Another cooling method is conduction cooling by a refrigerator. Because the superconducting coil is cooled only by the conduction from a cold head of the refrigerator, thermal conductivity of structural materials is very important from a viewpoint of stability of the coil.We propose a high thermal conduction plastic as the structural material whose name is a Dyneema fiber reinforce plastic (DFRP). DFRP has a characteristic of thermal expansion with decreasing of temperature. The small superconducting coils with DFRP bobbins were made and cooled by a refrigerator, and the coil stability was measured. The coil having the same specifications that made of aluminum nitride and glass fiber reinforced plastic (GFRP) were also made and stability were measured for the comparison.According to the experimental data, the heat transfer from the winding to the structural material became good in the condition with large coil winding tension, and the DFRP coil stability is similar or better than the AlN coil stability.